Solid state lighting (SSL) technology (such as light emitting diodes (LEDs)) is promising for lighting, illumination and display applications. Due to higher efficiency and longer life time compared with conventional incandescent and fluorescent lamps, costs of electricity consumption, replacement costs and maintenance costs can be significantly reduced by using SSL. Also, by using signal processing and control circuits to directly control pixels in an SSL display, the SSL technology may find wide applications in micro-display, projection display and other areas to achieve high performance, high efficiency and eco-friendly systems.
However, conventional solid state lightings have two critical issues: they are relatively expensive and bulky. Taking LED bulbs as an example, the price of LED bulbs can be many times more expensive than competing fluorescent bulbs. The top two contributors to the cost of LED bulbs are LED packaging and the driver module. A further drawback is that the driver module occupies a large volume. Typically, the circuit board for the driver module includes a power transformer, a power switch, several capacitors, and a controller. Further, passive components (transformer, capacitor) of the driver module also occupy a large volume (the large volume of the transformer is due to the reason that the offline voltage is relatively high (110 VAC˜220 VAC), so at tens of kHz range, the required inductance value of the transformer is large). These bulky driver circuits severely limit the application of SSL in applications where compactness is important.